The Mechanical Properties Of Polypropylene/Polylactic Acid (PP-PLA) Polymer Blends.
ii
DECLARATION
“I hereby declare that the work in this report is my own except for summaries and
quotations which have been duly acknowledged.”
Signature : ..............................................
Author
: FARHANA BTE MASRON
Date
: 30 JUNE 2012
iii
I dedicate this dissertation to my family, especially…
to Dad, Masron b. Ahmad Dasuki and
Mom, Habsah bt. Surip for instilling the importance of hard work
and higher education;
to friends, Narissa, Hafizah and Fakhrezah—may you also be motivated
and encouraged to reach your dreams;
finally to Hamzaitul Akmarizal,
thank you for your strength, support and inspiration.
iv
ACKNOWLEDGEMENTS
In the name of Allah, I was very thankful for His kindness that helps me a lot in
facing all challenges to make this project succeed.
A big thank you goes to my supervisor, Mr Mohd Nur Azmi bin Nordin for all
his guidance and also sharing knowledge and experiences that help me a lot in
completing this project smoothly. I also like to thank to all lecturers and staffs of Faculty
of Mechanical Engineering that involved directly or indirectly in giving helps, options
and ideas. Also, not forgotten, special thank to the lecturers and staffs of Faculty of
Manufacturing Engineering because of their help throughout in this project.
I am also obliged to everyone who had directly and indirectly involved in
contributing the ideas. Millions of appreciations to my beloved family for their moral
and materials support. I would like to thank all my friends for their support and giving
their constructive critics. With the support and love given by all of you, I hope I will
become a successful person and can contribute to my beloved country, Malaysia. Thank
you.
v
ABSTRACT
Polypropylene (PP) was chosen as raw material in this study due to low cost and
good mechanical properties. This factor encourages many researchers in many fields of
study to choose PP as the material. In the other side, PLA has advantage in degradability
because it is classified as a biodegradable polymer under specific condition. The
objective of this study is to produce the PP/PLA polymer blends. The purpose of
producing this polymer blends is to investigate the mechanical properties of PP/PLA
polymer blends by running several mechanical tests such as tensile, 3 points bending and
Charpy impact test. In this study, the specimens of PP/PLA polymer blends with
difference weight ratio were produced and the optimum weight ratio will be evaluated in
each mechanical test that had been done. Other than that, biodegradable test was run to
investigate the biodegradability of polymer blends and FTIR test to investigate the
bonding of new polymer blends. In this study, the specimens of the PP/PLA polymer
blends with the different weight percentage – PLA 5 wt%, 10 wt% and 15 wt %
produced by melting compound process. From the tensile test, PP/PLA 5 wt% had
higher tensile strength but same Young’s modulus with other blends. For flexural
properties, PP/PLA 10 wt% had highest flexural strength and modulus compared to Neat
PP and PP/PLA polymer blends. For impact strength, the PP/PLA blends had low impact
strength compared to Neat PP. For biodegradable test, PP/PLA polymer blends showed
that the blends had ability to biodegrade in specific condition for 8 weeks and PP/PLA
10 wt% showed the highest percentage of weight reduction which was 1.3%. Finally,
from the FTIR test, the chemical bonding of PP/PLA polymer blends showed that the
blends had combination of chemical bonding of PP and PLA.
vi
ABSTRAK
PP dipilih di dalam kajian ini kerana telah digunakan secara meluas di dalam
pelbagai bidang dan harganya yang rendah berbanding polimer lain sehingga telah
menarik minat banyak syarikat menggunakannya sebagai bahan mentah dalam
penghasilan produk mereka. Jika dilihat dari sudut berbeza, PLA pula mempunyai
kebolehan untuk terurai atau degradasi kerana PLA telah dikenalpasti sebagai polimer
biodegradasi sekiranya berada di dalam keadaan yang sesuai. Di dalam penyelidikan ini,
bahan uji kaji iaitu PP dan PLA polimer akan disatukan bersama dan akan dihasilkan
dengan nisbah berat yang berbeza antara PP dan PLA- 5 wt%, 10 wt% dan 15 wt%, dan
seterusnya nisbah berat optimum akan dinilai berdasarkan setiap keputusan ujian
mekanikal yang telah dijalankan. Ujian mekanikal yang dijalankan bertujuan untuk
mengkaji sifat-sifat mekanik dengan menjalankan ujian seperti ujian ketegangan,
kelenturan, hentaman Charpy dan kekerasan. Daripada kajian ini, PP/PLA 5 wt%
mempunyai kekuatan tegangan yang paling tinggi tetapi nilai modulus Young yang sama
dengan komposis lain. Untuk ujian lenturan, PP/PLA 10 wt% mempunyai nilai
ketagangan lenturan yang paling tinggi berbanding komposisi lain. Daripada kajian ini.
Kebolehan biodegradasi oleh PLA telah menyebabkan campuran polimer PP/PLA juga
mewarisi sifat biodegradasinya. Kaedah “Fourier Transform Infrared Radiation” (FTIR)
dijalankan untuk mengkaji keterlarutan campuran yg telah dihasilan. Istilah keterlarut
campuran adalah penting untuk menganalpasti jenis ikatan kimia polimer. Jenis ikatan
kimia ini akan memberi kesan kepada sifat-sifat mekanik.
vii
TABLE OF CONTENTS
CHAPTER
TITLE
PAGE
TITLE PAGE
i
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENTS
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENTS
vii
LISTS OF FIGURE
CHAPTER 1
x
LIST OF TABLE
xiv
LIST OF ABBREVIATION AND SYMBOLS
xv
INTRODUCTION
1.1 BACKGROUND
1
1.1.1 Polymer
1
1.1.2 Crystallinity In Polymers
2
1.1.3 Melting Temperature, T m and Glass Transition
6
Temperature, T g in Polymers
1.1.4 Polymer blends
8
1.1.5 Polypropylene (PP)
10
1.1.6 Polylactide (PLA)
14
1.2 PROBLEM STATEMENTS
17
1.3 OBJECTIVE
18
1.4 SCOPE
18
viii
CHAPTER
TITLE
CHAPTER 2
LITERATURE REVIEW
2.1 INTRODUCTION
CHAPTER 4
19
2.1.1 Tensile and Flexural Test
19
2.1.2 Charpy Impact Test
26
2.2 BIODEGRADABLE POLYMERS
28
2.2.1 Biodegradation of PLA
29
2.3 FTIR SPECTROSCOPY
CHAPTER 3
PAGE
31
METHODOLOGY
3.1 INTRODUCTION
35
3.2 MATERIALS
36
3.3 SAMPLES PREPARATION
37
3.3.1 PP/PLA Specimens
37
3.3.2 Neat PP Specimens
43
3.4 MECHANICAL TEST
43
3.4.1 Tensile Test
43
3.4.2 Flexure Test
44
3.4.2 Charpy Impact Test
45
3.5 BIODEGRADABLE TEST
46
3.6 FTIR TEST
47
RESULT AND ANALYSIS
4.1 INTRODUCTION
48
4.2 TENSILE TEST RESULT
48
4.3 FLEXURAL TEST RESULT
54
4.4 CHARPY IMPACT TEST
59
4.5 BIODEGRADABLE TEST
60
4.6 FTIR SPECTROSCOPY
60
ix
CHAPTER
TITLE
CHAPTER 5
DISCUSSION
CHAPTER 6
PAGE
5.1 INTRODUCTION
63
5.2 TENSILE AND FLEXURAL PROPERTIES
63
5.3 IMPACT STRENGTH
68
5.4 BIODEGRADABILITY
69
5.5 FTIR SPECTROSCOPY
70
CONCLUSION AND RECOMMENDATION
6.1 CONCLUSION
68
6.2 RECOMMENDATION `
69
REFERENCES
73
APPENDIX
78
x
LIST OF FIGURES
FIGURE TITLE
1.1
Schematic illustration of molecular structure of polymers (a)
PAGE
2
linear, (b) branched, (c) cross-linked and (d) network
1.2
Crystalline and amorphous region in polymer
3
1.3
Schematic of detailed structure of a spherulite
4
1.4
Stages in the deformation of semicrystalline polymer. (a) Two
5
adjacent chain folded lamellea and interlamellar amorphous
material before deformation. (b) Elongation of amorphous tie
chains during first stage of deformation. (c) Tilting of lamellar
chain folds during the second stage. (d) Separation of the
crytalline block segments during the third stage. (e) Orientation
of block segments and tie chains with the tensile axis in final
stage
1.5
Specific volume versus temperature for amorphous (curve A),
7
semicrystalline (curve B) and cystalline (curve C)
1.6
Monomer of PP
10
1.7
Monomer of propylene become polypropylene after
10
polymerization
1.8 (a)
Schematics of metallocene catalyst
11
1.8 (b)
Ziegler-Natta catalyst
11
1.9
Mechanism of Ziegler-Natta polymerization process
11
1.10
Tacticity of Polymer
12
1.11
Production of PLA
14
1.12
From left: D-lactide, L-lactide and Meso-lactide
15
xi
2.1
Universal Tensile Test Machine
20
2.2
Tensile Test Specimens
20
2.3
Stress vs strain curve for tensile test
21
2.4
Tensile strengths of metals, ceramics, polymer and
22
composites/fibers
2.5
Flexural test specimens in testing machine
23
2.6
Tensile strength and modulus for PP/lignin blends
24
2.7
Flexural strength and modulus for PP/lignin blends
24
2.8
Stress-strain curves for PLA/PCL blends
25
2.9
Flexural strength of PLA/PCL blends
25
2.10
Charpy Impact test instrument
26
2.11
Classification of Biodegradable Polymers
28
2.12
PLA hydrolysis and molecular weight loss
30
2.13
Degradation of PLA under landfill condition
31
2.14
Wavenumber at characteristic frequencies
32
2.15
Wavenumber of PP using FTIR
33
2.16
Wavenumber of lactic acid (LA) and PLA using FTIR
34
3.1
Flow Chart of the fabrication process
36
3.2
HAAKE Internal Mixer
38
3.3 (a)
Compound of PP/PLA polymer blends
38
3.3 (b)
Pellet size of PP/PLA polymer blends
38
3.4
Crusher Machine
39
3.5
Pellet size of PP/PLA compound placed in mold
39
3.6
Hot Press Machine
40
3.7
Plate shape of PP/PLA polymer blends
40
3.8
Sample Cutter Machine
41
3.9 (a)
Dimension of tensile test specimen
41
3.9 (b)
Specimen of tensile test
41
3.10 (a)
Dimension for bending test
42
3.10 (b)
Specimen for bending test
42
3.11 (a)
Dimension of Charpy Impact test
42
xii
3.11 (b)
Specimen of Charpy Impact test
42
3.12
Shimadzu Universal Testing Machine
43
3.13 (a)
Specimen during testing
44
3.13 (b)
Specimen after break
44
3.14
Specimen of bending test during testing
45
3.15
Charpy Impact Tester
45
3.16
Samples placed before buried in soil for biodegradable test
46
3.17
PerkinElmer Spectrum 100 FTIR Spectrometer
47
4.1
Stress-strain diagrams for Neat PP specimens
49
4.2
Stress-strain diagrams for PP/PLA 5 wt% specimens
50
4.3
Stress-strain diagrams for PP/PLA 10 wt% specimens
52
4.4
Stress-strain diagrams for PP/PLA 15 wt% specimens
53
4.5
Stress-strain diagrams for Neat PP specimens
54
4.6
Stress-strain diagrams for PP/PLA 5 wt% specimens
55
4.7
Graph of stress versus strain for PP/PLA 10 wt% specimens
57
4.8
Stress versus strain for PP/PLA 15 wt% specimens
58
4.9
FTIR spectra for Neat PP
61
4.10
FTIR spectra for Neat PLA
61
5.1
Stress-strain diagrams for Neat PP, PP/PLA 5 wt%, PP/PLA 10 64
wt% and PP/PLA 15 wt% specimens
5.2
Graph of tensile strength and Young’s modulus for Neat PP,
65
PP/PLA 5 wt%, PP/PLA 10 wt% and PP/PLA 15 wt%
5.3
Stress-strain diagrams for Neat PP, PP/PLA 5 wt%, PP/PLA 10 66
wt% and PP/PLA 15 wt% specimens
5.4
Graph of flexural strength and flexural modulus for Neat PP,
67
PP/PLA 5 wt%, PP/PLA 10 wt% and PP/PLA 15 wt%
5.5
Graph of average impact energy for Neat PP, PP/PLA 5 wt%,
68
PP/PLA 10 wt% and PP/PLA 15 wt %
5.6
Graph of different weight percentage of Neat PP, PP/PLA 3
wt%, PP/PLA 5 wt%, PP/PLA 10 wt% and PP/PLA 15 wt%
specimens
69
xiii
5.7
FTIR spectra for Neat PP, PP/PLA 5 wt%, PP/PLA 10 wt%
and PP/PLA 15 wt%
70
xiv
LIST OF TABLES
TABLE
1.1
TITLE
Melting and Glass Transition Temperatures for Some of
PAGE
8
Common Polymeric Materials
1.2
Mechanical properties
13
1.3
Mechanical properties of PLA
16
3.1
Properties of PP and PLA
37
3.2
Weight percentage (wt%) of PP and PLA for each type
37
specimen
3.3
Weight of specimens for biodegradable test
46
4.1
Tensile properties for Neat PP specimen
49
4.2
Tensile properties for PP/PLA 5 wt% specimens
51
4.3
Tensile properties for PP/PLA 10 wt % specimens
52
4.4
Tensile properties for PP/PLA 15 wt% specimens
53
4.5
Flexural properties for Neat PP specimens
55
4.6
Flexural properties for PP/PLA 5 wt% specimens
56
4.7
Flexural properties for PP/PLA 10 wt% specimens
57
4.8
Flexural properties for PP/PLA 15 wt% specimens
58
4.9
Energy absorb by the Neat PP, PP/PLA 5 wt%, PP/PLA 10
59
wt% and PP/PLA 15 wt% specimens
4.10
Weight of Neat PP, PP/PLA 3 wt%, PP/PLA 5 wt%, PP/PLA
10wt % and
5.1
60
PP/PLA 15 wt% specimens for eight weeks
Tensile properties for Neat PP, PP/PLA 5 wt%, PP/PLA 10
64
wt% and PP/PLA 15 wt % specimens
5.2
Average flexural strength, strain and flexural modulus for Neat
PP, PP/PLA 5 wt%, PP/PLA 10 wt% and PP/PLA 15 wt%.
66
xv
LIST OF ABBREVIATION AND SYMBOL
PP
=
Polypropylene
PLA
=
Polylactic Acid
PE
=
Polyethylene
PS
=
Polystyrene
HDPE
=
High Density Polyethylene
LDPE
=
Low Density Polyethylene
PPO
=
poly(dimethylphenylene oxide
UV
=
Ultra Violet
EPDM
=
Ethylene–Propylene–Diene Elastomer
FTIR
=
Fourier Transform Infra Red
SDN.BHD.
=
Sendirian Berhad
Tm
=
Melting temperature
Tg
=
Glass Temperature
m
=
Meter
mm
=
milimeter
g
=
gram
°C
=
degree Celcius
σ
=
Stress
E
=
Young’s modulus
wt%
=
weight percentage
1
CHAPTER 1
INTRODUCTION
1.1
BACKGROUND
1.1.1
POLYMER
Polymer is a particular class of macro-molecules that consist of repeated
chemical units, also called monomer, joined end to end, or possible in more complicated
ways by covalent bonds to form a chain molecule. In a simple word, polymer means a
chain of monomers repeated and linked with each other to produce a long chain. If there
are only one monomer repeated in a chain, it is called homopolymer but copolymer
occur when more than one monomer present. Carbon and hydrogen are the most
common atoms in monomer but other atom may be present such as oxygen, nitrogen,
and silicon. Some of the common polymers are polyethylene (PE), polystyrene (PS) and
polypropylene (PP) [1]. Polymers also has many possible classification which are the
type of polymerization process used to process them, structure of the polymer whether it
is linear, branched or network polymer, and also based on their properties whether it is
thermoplastics or thermosetting [2].
Figure 1.1 below represents the type of molecular structure of polymers. If
monomers linked end to end in single chain, it called linear polymer. Polyethylene is an
example of linear polymer. Branched polymer has molecular structure where the side-
2
branch chains connected to the main chain. In cross-linked polymer, a few linear chains
are joined together at various positions by covalent bonds such as rubber. The term of
network polymer is when multifunctional monomers that have three or more active
covalent bands form three dimensional networks and epoxies belong to this group [3].
Figure 1.1 Schematic illustration of molecular structure of polymers (a) linear, (b)
branched, (c) cross-linked and (d) network [4]
Linear and branched polymers form a class of materials known as thermoplastic.
A thermoplastic material is a high molecular weight polymer that is not cross linked.
That is why these materials flow when give heat and can be molded into many shapes
which they retain when cool but differ with the thermosetting materials. A thermosetting
material is a heavy cross-linking material and once the cross-links form; these polymers
cannot be changed anymore without destroying the plastics.
1.1.2
CRYSTALLINITY IN POLYMERS
Polymers exist both in crystalline and amorphous region and this is called
semicrystalline material. Crystalline region exists when the molecular chains packed in
ordered arrangement and amorphous region exist in between these crystalline region
which are arranged in disorganized state. Crystallinity is an indication of amount of
crystalline region respect to amorphous region in polymer. Figure 1.2 illustrate the
crystalline and amorphous region in polymer.When crystallinity increased, the rigidity,
3
tensile strength and opacity (due to light scattering) also increased. Amorphous
polymers are usually less rigid, easily to deformed and often transparent. The factors
that influence the degree of crystallinity are chain length, chain branching and interchain
bonding. Crystallinity in a polymer is very important in order to determine its properties.
The more crystalline region in the polymer, the stronger and less flexible it become.
Figure 1.2 Crystalline and amorphous region in polymer [3]
For example, high density polyethylene (HDPE) form from very long
unbranched hydrocarbon chains. These chains pack together easily in crystalline region
and also alternate with amorphous region and finally produce the relatively strong and
stiff. Compared to the low density polyethylene (LDPE) that form from smaller and
many branched chains, these do not easily adopt crystalline structures. This polymer is
softer, weaker, low density and easily deformed compared to HDPE. As a result,
mechanical properties such as ductility, tensile strenght and hardness rise directly
proportional to tha chain length [4].
Many polymers crystallized from a melt will form spherulites and each sperulites
may grow to be spherical in shape and consist of lamellar such illustrated in Figure 1.3.
Lamellar is the crystlline portion and the outside of lamellar is amorphous region. The
lamellar crystals grows from center of spherullite [5]. To pass through amorphous
4
region, tie-chain molecules act as connecting links between adjacent lamellar. The
surface of adjacent spherullites start to impinge on one another when the crystallization
of a spherullitic structure near completion.
Figure 1.3 Schematic of detailed structure of a spherulite [4]
If tensile load applied to the semicrystalline polymer, two adjacent chain-folded
lamellar and interlamellar amorphous tend to deform in Figure 1.4 (a). The lamellar will
slide each other within the amorphous region become extended in the initial stage as
shows in Figure 1.4 (b). In a period of time, the deformation continued and chain folds
become aligned with the tensile axis as in Figure 1.4 (c). If more load given, separation
between crystalline segments occurred showed in Figure 1.4 (d). Finally, the blocks and
tie chains aligned along the direction of tensile axis as in Figure 1.4 (e). Thus, this is
5
important to choose the right polymer because each polymer has different crystallinity
and also has different properties.
Figure 1.4 Stages in the deformation of semicrystalline polymer. (a) Two adjacent chain
folded lamellea and interlamellar amorphous material before deformation. (b)
Elongation of amorphous tie chains during first stage of deformation. (c) Tilting of
lamellar chain folds during the second stage. (d) Separation of the crytalline block
segments during the third stage. (e) Orientation of block segments and tie chains with
the tensile axis in final stage [4]
6
1.1.3
MELTING TEMPERATURE, T m AND GLASS TRANSITION
TEMPERATURE, T g IN POLYMER
At the melting temperature, T m , the crystalline of polymers will lose their
structure or melt. T m depends on crystallinity, if crystallinity increases so does T m . The
melting of polymers takes place over a range of temperatures. The melting behaviour
depends on temperature which it crystallizes. Impurities in the polymers also decrease
the melting temperature.
The stiffness of the chain controlled by the ease of rotation about the chemical
bonds along the chain give the huge effect. The chain flexibility can be lower by the
presence of double bonds and aromatic groups in the polymer backbone and finally
increase the T m . The size and type of side groups influence the chain rotational freedom
and flexibility and raise of T m . Table 1.1 showed that PP has a higher T m than PE which
are 175°C and 115°C respectively. It is because methyl group in PP is larger than the
hydrogen atom in PE and this increase the T m [3].
Glass temperature, T g is the temperature where the polymers lose their structural
mobility of polymer chains and become rigid glass.
The polymer will behave in
increasingly brittle manner if the temperature drops below T g and becomes more rubberlike if the temperature rise aboveT g . The T g also known as the temperature at which the
molecules of the material move enough so that can be processed and polymers tend to be
brittle below the T g [6]. The value of T g depends on molecular characteristics that affect
chain stiffness, and all factors are same as the T m . Thus, T m and T g is important during
selecting materials for various applications.
Figure 1.5 is the T m and T g for amorphous, semicrystalline and crystalline
materials respectively. For crystalline material (curve C), there is discontinuous changes
in specific volume at T m while the amorphous material (curve A), the curve is
continuous. For the semicrystalline materials, the behaviour is intermediate between
crystalline and amorphous [4].
7
Melting process involves the breaking of inter-chain bonds, so the glass and
melting temperature depend on chain stiffness, molecular shape and size, side branches
and cross-linking [5]. The right temperature must be setup because high temperature
may degrade the polymer or destroy the chain and additives may decompose. If
temperature is too low, the structure fails to achieve the required homogeneity and thus
will reduce impact resistance [6]. Dwell time in process also play crucial role. If higher
dwell time given, thermal decomposition may take place even the melt temperature is
correct but if too short, the melt will not have time to fully homogeneous.
Figure 1.5 Specific volume versus temperature for amorphous (curve A), semicrystalline
(curve B) and cystalline (curve C)[4]
8
Table 1.1 Melting and Glass Transition Temperatures for Some of Common Polymeric
Materials [3,9]
Polymers
1.1.4
T m (ºC)
T g (ºC)
Polypropylene (PP)
165
-18
Poly-lactic Acid (PLA)
175
55 - 60
Polyethylene (PE)
115
110
Polytetrafluoroethylene (PTFE)
327
-97
Polystyrene (PS)
240
100
Polycarbonate (PC)
265
150
POLYMER BLENDS
Polymer blends occur when two or more different polymers mixed together.
There are two types of polymer blends which are miscible and immiscible polymer
blends. For miscible polymer blends, the miscibility and homogeneity extend down to
the molecular lever which is no phase separation occur to the polymer. For immiscible
polymer blends, there are phase separations occurs and sometimes called compatible
blends. The compatible blends are also polymer alloy [11,14]. The light scattering, Xray scattering, and neutron scattering can be used in order to investigate the phase of
polymer blends.
In polymer blends, there are either homogenous or heterogeneous miscibility.
Both polymers lose their identity and usually the new properties are arithmetical average
of the polymer in homogeneous but in heterogeneous, the properties for involved
polymers are present [12]. The weakness of the one polymer can affect the strengths of
the polymer. But still, the blends can have better properties than individual element.
DECLARATION
“I hereby declare that the work in this report is my own except for summaries and
quotations which have been duly acknowledged.”
Signature : ..............................................
Author
: FARHANA BTE MASRON
Date
: 30 JUNE 2012
iii
I dedicate this dissertation to my family, especially…
to Dad, Masron b. Ahmad Dasuki and
Mom, Habsah bt. Surip for instilling the importance of hard work
and higher education;
to friends, Narissa, Hafizah and Fakhrezah—may you also be motivated
and encouraged to reach your dreams;
finally to Hamzaitul Akmarizal,
thank you for your strength, support and inspiration.
iv
ACKNOWLEDGEMENTS
In the name of Allah, I was very thankful for His kindness that helps me a lot in
facing all challenges to make this project succeed.
A big thank you goes to my supervisor, Mr Mohd Nur Azmi bin Nordin for all
his guidance and also sharing knowledge and experiences that help me a lot in
completing this project smoothly. I also like to thank to all lecturers and staffs of Faculty
of Mechanical Engineering that involved directly or indirectly in giving helps, options
and ideas. Also, not forgotten, special thank to the lecturers and staffs of Faculty of
Manufacturing Engineering because of their help throughout in this project.
I am also obliged to everyone who had directly and indirectly involved in
contributing the ideas. Millions of appreciations to my beloved family for their moral
and materials support. I would like to thank all my friends for their support and giving
their constructive critics. With the support and love given by all of you, I hope I will
become a successful person and can contribute to my beloved country, Malaysia. Thank
you.
v
ABSTRACT
Polypropylene (PP) was chosen as raw material in this study due to low cost and
good mechanical properties. This factor encourages many researchers in many fields of
study to choose PP as the material. In the other side, PLA has advantage in degradability
because it is classified as a biodegradable polymer under specific condition. The
objective of this study is to produce the PP/PLA polymer blends. The purpose of
producing this polymer blends is to investigate the mechanical properties of PP/PLA
polymer blends by running several mechanical tests such as tensile, 3 points bending and
Charpy impact test. In this study, the specimens of PP/PLA polymer blends with
difference weight ratio were produced and the optimum weight ratio will be evaluated in
each mechanical test that had been done. Other than that, biodegradable test was run to
investigate the biodegradability of polymer blends and FTIR test to investigate the
bonding of new polymer blends. In this study, the specimens of the PP/PLA polymer
blends with the different weight percentage – PLA 5 wt%, 10 wt% and 15 wt %
produced by melting compound process. From the tensile test, PP/PLA 5 wt% had
higher tensile strength but same Young’s modulus with other blends. For flexural
properties, PP/PLA 10 wt% had highest flexural strength and modulus compared to Neat
PP and PP/PLA polymer blends. For impact strength, the PP/PLA blends had low impact
strength compared to Neat PP. For biodegradable test, PP/PLA polymer blends showed
that the blends had ability to biodegrade in specific condition for 8 weeks and PP/PLA
10 wt% showed the highest percentage of weight reduction which was 1.3%. Finally,
from the FTIR test, the chemical bonding of PP/PLA polymer blends showed that the
blends had combination of chemical bonding of PP and PLA.
vi
ABSTRAK
PP dipilih di dalam kajian ini kerana telah digunakan secara meluas di dalam
pelbagai bidang dan harganya yang rendah berbanding polimer lain sehingga telah
menarik minat banyak syarikat menggunakannya sebagai bahan mentah dalam
penghasilan produk mereka. Jika dilihat dari sudut berbeza, PLA pula mempunyai
kebolehan untuk terurai atau degradasi kerana PLA telah dikenalpasti sebagai polimer
biodegradasi sekiranya berada di dalam keadaan yang sesuai. Di dalam penyelidikan ini,
bahan uji kaji iaitu PP dan PLA polimer akan disatukan bersama dan akan dihasilkan
dengan nisbah berat yang berbeza antara PP dan PLA- 5 wt%, 10 wt% dan 15 wt%, dan
seterusnya nisbah berat optimum akan dinilai berdasarkan setiap keputusan ujian
mekanikal yang telah dijalankan. Ujian mekanikal yang dijalankan bertujuan untuk
mengkaji sifat-sifat mekanik dengan menjalankan ujian seperti ujian ketegangan,
kelenturan, hentaman Charpy dan kekerasan. Daripada kajian ini, PP/PLA 5 wt%
mempunyai kekuatan tegangan yang paling tinggi tetapi nilai modulus Young yang sama
dengan komposis lain. Untuk ujian lenturan, PP/PLA 10 wt% mempunyai nilai
ketagangan lenturan yang paling tinggi berbanding komposisi lain. Daripada kajian ini.
Kebolehan biodegradasi oleh PLA telah menyebabkan campuran polimer PP/PLA juga
mewarisi sifat biodegradasinya. Kaedah “Fourier Transform Infrared Radiation” (FTIR)
dijalankan untuk mengkaji keterlarutan campuran yg telah dihasilan. Istilah keterlarut
campuran adalah penting untuk menganalpasti jenis ikatan kimia polimer. Jenis ikatan
kimia ini akan memberi kesan kepada sifat-sifat mekanik.
vii
TABLE OF CONTENTS
CHAPTER
TITLE
PAGE
TITLE PAGE
i
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENTS
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENTS
vii
LISTS OF FIGURE
CHAPTER 1
x
LIST OF TABLE
xiv
LIST OF ABBREVIATION AND SYMBOLS
xv
INTRODUCTION
1.1 BACKGROUND
1
1.1.1 Polymer
1
1.1.2 Crystallinity In Polymers
2
1.1.3 Melting Temperature, T m and Glass Transition
6
Temperature, T g in Polymers
1.1.4 Polymer blends
8
1.1.5 Polypropylene (PP)
10
1.1.6 Polylactide (PLA)
14
1.2 PROBLEM STATEMENTS
17
1.3 OBJECTIVE
18
1.4 SCOPE
18
viii
CHAPTER
TITLE
CHAPTER 2
LITERATURE REVIEW
2.1 INTRODUCTION
CHAPTER 4
19
2.1.1 Tensile and Flexural Test
19
2.1.2 Charpy Impact Test
26
2.2 BIODEGRADABLE POLYMERS
28
2.2.1 Biodegradation of PLA
29
2.3 FTIR SPECTROSCOPY
CHAPTER 3
PAGE
31
METHODOLOGY
3.1 INTRODUCTION
35
3.2 MATERIALS
36
3.3 SAMPLES PREPARATION
37
3.3.1 PP/PLA Specimens
37
3.3.2 Neat PP Specimens
43
3.4 MECHANICAL TEST
43
3.4.1 Tensile Test
43
3.4.2 Flexure Test
44
3.4.2 Charpy Impact Test
45
3.5 BIODEGRADABLE TEST
46
3.6 FTIR TEST
47
RESULT AND ANALYSIS
4.1 INTRODUCTION
48
4.2 TENSILE TEST RESULT
48
4.3 FLEXURAL TEST RESULT
54
4.4 CHARPY IMPACT TEST
59
4.5 BIODEGRADABLE TEST
60
4.6 FTIR SPECTROSCOPY
60
ix
CHAPTER
TITLE
CHAPTER 5
DISCUSSION
CHAPTER 6
PAGE
5.1 INTRODUCTION
63
5.2 TENSILE AND FLEXURAL PROPERTIES
63
5.3 IMPACT STRENGTH
68
5.4 BIODEGRADABILITY
69
5.5 FTIR SPECTROSCOPY
70
CONCLUSION AND RECOMMENDATION
6.1 CONCLUSION
68
6.2 RECOMMENDATION `
69
REFERENCES
73
APPENDIX
78
x
LIST OF FIGURES
FIGURE TITLE
1.1
Schematic illustration of molecular structure of polymers (a)
PAGE
2
linear, (b) branched, (c) cross-linked and (d) network
1.2
Crystalline and amorphous region in polymer
3
1.3
Schematic of detailed structure of a spherulite
4
1.4
Stages in the deformation of semicrystalline polymer. (a) Two
5
adjacent chain folded lamellea and interlamellar amorphous
material before deformation. (b) Elongation of amorphous tie
chains during first stage of deformation. (c) Tilting of lamellar
chain folds during the second stage. (d) Separation of the
crytalline block segments during the third stage. (e) Orientation
of block segments and tie chains with the tensile axis in final
stage
1.5
Specific volume versus temperature for amorphous (curve A),
7
semicrystalline (curve B) and cystalline (curve C)
1.6
Monomer of PP
10
1.7
Monomer of propylene become polypropylene after
10
polymerization
1.8 (a)
Schematics of metallocene catalyst
11
1.8 (b)
Ziegler-Natta catalyst
11
1.9
Mechanism of Ziegler-Natta polymerization process
11
1.10
Tacticity of Polymer
12
1.11
Production of PLA
14
1.12
From left: D-lactide, L-lactide and Meso-lactide
15
xi
2.1
Universal Tensile Test Machine
20
2.2
Tensile Test Specimens
20
2.3
Stress vs strain curve for tensile test
21
2.4
Tensile strengths of metals, ceramics, polymer and
22
composites/fibers
2.5
Flexural test specimens in testing machine
23
2.6
Tensile strength and modulus for PP/lignin blends
24
2.7
Flexural strength and modulus for PP/lignin blends
24
2.8
Stress-strain curves for PLA/PCL blends
25
2.9
Flexural strength of PLA/PCL blends
25
2.10
Charpy Impact test instrument
26
2.11
Classification of Biodegradable Polymers
28
2.12
PLA hydrolysis and molecular weight loss
30
2.13
Degradation of PLA under landfill condition
31
2.14
Wavenumber at characteristic frequencies
32
2.15
Wavenumber of PP using FTIR
33
2.16
Wavenumber of lactic acid (LA) and PLA using FTIR
34
3.1
Flow Chart of the fabrication process
36
3.2
HAAKE Internal Mixer
38
3.3 (a)
Compound of PP/PLA polymer blends
38
3.3 (b)
Pellet size of PP/PLA polymer blends
38
3.4
Crusher Machine
39
3.5
Pellet size of PP/PLA compound placed in mold
39
3.6
Hot Press Machine
40
3.7
Plate shape of PP/PLA polymer blends
40
3.8
Sample Cutter Machine
41
3.9 (a)
Dimension of tensile test specimen
41
3.9 (b)
Specimen of tensile test
41
3.10 (a)
Dimension for bending test
42
3.10 (b)
Specimen for bending test
42
3.11 (a)
Dimension of Charpy Impact test
42
xii
3.11 (b)
Specimen of Charpy Impact test
42
3.12
Shimadzu Universal Testing Machine
43
3.13 (a)
Specimen during testing
44
3.13 (b)
Specimen after break
44
3.14
Specimen of bending test during testing
45
3.15
Charpy Impact Tester
45
3.16
Samples placed before buried in soil for biodegradable test
46
3.17
PerkinElmer Spectrum 100 FTIR Spectrometer
47
4.1
Stress-strain diagrams for Neat PP specimens
49
4.2
Stress-strain diagrams for PP/PLA 5 wt% specimens
50
4.3
Stress-strain diagrams for PP/PLA 10 wt% specimens
52
4.4
Stress-strain diagrams for PP/PLA 15 wt% specimens
53
4.5
Stress-strain diagrams for Neat PP specimens
54
4.6
Stress-strain diagrams for PP/PLA 5 wt% specimens
55
4.7
Graph of stress versus strain for PP/PLA 10 wt% specimens
57
4.8
Stress versus strain for PP/PLA 15 wt% specimens
58
4.9
FTIR spectra for Neat PP
61
4.10
FTIR spectra for Neat PLA
61
5.1
Stress-strain diagrams for Neat PP, PP/PLA 5 wt%, PP/PLA 10 64
wt% and PP/PLA 15 wt% specimens
5.2
Graph of tensile strength and Young’s modulus for Neat PP,
65
PP/PLA 5 wt%, PP/PLA 10 wt% and PP/PLA 15 wt%
5.3
Stress-strain diagrams for Neat PP, PP/PLA 5 wt%, PP/PLA 10 66
wt% and PP/PLA 15 wt% specimens
5.4
Graph of flexural strength and flexural modulus for Neat PP,
67
PP/PLA 5 wt%, PP/PLA 10 wt% and PP/PLA 15 wt%
5.5
Graph of average impact energy for Neat PP, PP/PLA 5 wt%,
68
PP/PLA 10 wt% and PP/PLA 15 wt %
5.6
Graph of different weight percentage of Neat PP, PP/PLA 3
wt%, PP/PLA 5 wt%, PP/PLA 10 wt% and PP/PLA 15 wt%
specimens
69
xiii
5.7
FTIR spectra for Neat PP, PP/PLA 5 wt%, PP/PLA 10 wt%
and PP/PLA 15 wt%
70
xiv
LIST OF TABLES
TABLE
1.1
TITLE
Melting and Glass Transition Temperatures for Some of
PAGE
8
Common Polymeric Materials
1.2
Mechanical properties
13
1.3
Mechanical properties of PLA
16
3.1
Properties of PP and PLA
37
3.2
Weight percentage (wt%) of PP and PLA for each type
37
specimen
3.3
Weight of specimens for biodegradable test
46
4.1
Tensile properties for Neat PP specimen
49
4.2
Tensile properties for PP/PLA 5 wt% specimens
51
4.3
Tensile properties for PP/PLA 10 wt % specimens
52
4.4
Tensile properties for PP/PLA 15 wt% specimens
53
4.5
Flexural properties for Neat PP specimens
55
4.6
Flexural properties for PP/PLA 5 wt% specimens
56
4.7
Flexural properties for PP/PLA 10 wt% specimens
57
4.8
Flexural properties for PP/PLA 15 wt% specimens
58
4.9
Energy absorb by the Neat PP, PP/PLA 5 wt%, PP/PLA 10
59
wt% and PP/PLA 15 wt% specimens
4.10
Weight of Neat PP, PP/PLA 3 wt%, PP/PLA 5 wt%, PP/PLA
10wt % and
5.1
60
PP/PLA 15 wt% specimens for eight weeks
Tensile properties for Neat PP, PP/PLA 5 wt%, PP/PLA 10
64
wt% and PP/PLA 15 wt % specimens
5.2
Average flexural strength, strain and flexural modulus for Neat
PP, PP/PLA 5 wt%, PP/PLA 10 wt% and PP/PLA 15 wt%.
66
xv
LIST OF ABBREVIATION AND SYMBOL
PP
=
Polypropylene
PLA
=
Polylactic Acid
PE
=
Polyethylene
PS
=
Polystyrene
HDPE
=
High Density Polyethylene
LDPE
=
Low Density Polyethylene
PPO
=
poly(dimethylphenylene oxide
UV
=
Ultra Violet
EPDM
=
Ethylene–Propylene–Diene Elastomer
FTIR
=
Fourier Transform Infra Red
SDN.BHD.
=
Sendirian Berhad
Tm
=
Melting temperature
Tg
=
Glass Temperature
m
=
Meter
mm
=
milimeter
g
=
gram
°C
=
degree Celcius
σ
=
Stress
E
=
Young’s modulus
wt%
=
weight percentage
1
CHAPTER 1
INTRODUCTION
1.1
BACKGROUND
1.1.1
POLYMER
Polymer is a particular class of macro-molecules that consist of repeated
chemical units, also called monomer, joined end to end, or possible in more complicated
ways by covalent bonds to form a chain molecule. In a simple word, polymer means a
chain of monomers repeated and linked with each other to produce a long chain. If there
are only one monomer repeated in a chain, it is called homopolymer but copolymer
occur when more than one monomer present. Carbon and hydrogen are the most
common atoms in monomer but other atom may be present such as oxygen, nitrogen,
and silicon. Some of the common polymers are polyethylene (PE), polystyrene (PS) and
polypropylene (PP) [1]. Polymers also has many possible classification which are the
type of polymerization process used to process them, structure of the polymer whether it
is linear, branched or network polymer, and also based on their properties whether it is
thermoplastics or thermosetting [2].
Figure 1.1 below represents the type of molecular structure of polymers. If
monomers linked end to end in single chain, it called linear polymer. Polyethylene is an
example of linear polymer. Branched polymer has molecular structure where the side-
2
branch chains connected to the main chain. In cross-linked polymer, a few linear chains
are joined together at various positions by covalent bonds such as rubber. The term of
network polymer is when multifunctional monomers that have three or more active
covalent bands form three dimensional networks and epoxies belong to this group [3].
Figure 1.1 Schematic illustration of molecular structure of polymers (a) linear, (b)
branched, (c) cross-linked and (d) network [4]
Linear and branched polymers form a class of materials known as thermoplastic.
A thermoplastic material is a high molecular weight polymer that is not cross linked.
That is why these materials flow when give heat and can be molded into many shapes
which they retain when cool but differ with the thermosetting materials. A thermosetting
material is a heavy cross-linking material and once the cross-links form; these polymers
cannot be changed anymore without destroying the plastics.
1.1.2
CRYSTALLINITY IN POLYMERS
Polymers exist both in crystalline and amorphous region and this is called
semicrystalline material. Crystalline region exists when the molecular chains packed in
ordered arrangement and amorphous region exist in between these crystalline region
which are arranged in disorganized state. Crystallinity is an indication of amount of
crystalline region respect to amorphous region in polymer. Figure 1.2 illustrate the
crystalline and amorphous region in polymer.When crystallinity increased, the rigidity,
3
tensile strength and opacity (due to light scattering) also increased. Amorphous
polymers are usually less rigid, easily to deformed and often transparent. The factors
that influence the degree of crystallinity are chain length, chain branching and interchain
bonding. Crystallinity in a polymer is very important in order to determine its properties.
The more crystalline region in the polymer, the stronger and less flexible it become.
Figure 1.2 Crystalline and amorphous region in polymer [3]
For example, high density polyethylene (HDPE) form from very long
unbranched hydrocarbon chains. These chains pack together easily in crystalline region
and also alternate with amorphous region and finally produce the relatively strong and
stiff. Compared to the low density polyethylene (LDPE) that form from smaller and
many branched chains, these do not easily adopt crystalline structures. This polymer is
softer, weaker, low density and easily deformed compared to HDPE. As a result,
mechanical properties such as ductility, tensile strenght and hardness rise directly
proportional to tha chain length [4].
Many polymers crystallized from a melt will form spherulites and each sperulites
may grow to be spherical in shape and consist of lamellar such illustrated in Figure 1.3.
Lamellar is the crystlline portion and the outside of lamellar is amorphous region. The
lamellar crystals grows from center of spherullite [5]. To pass through amorphous
4
region, tie-chain molecules act as connecting links between adjacent lamellar. The
surface of adjacent spherullites start to impinge on one another when the crystallization
of a spherullitic structure near completion.
Figure 1.3 Schematic of detailed structure of a spherulite [4]
If tensile load applied to the semicrystalline polymer, two adjacent chain-folded
lamellar and interlamellar amorphous tend to deform in Figure 1.4 (a). The lamellar will
slide each other within the amorphous region become extended in the initial stage as
shows in Figure 1.4 (b). In a period of time, the deformation continued and chain folds
become aligned with the tensile axis as in Figure 1.4 (c). If more load given, separation
between crystalline segments occurred showed in Figure 1.4 (d). Finally, the blocks and
tie chains aligned along the direction of tensile axis as in Figure 1.4 (e). Thus, this is
5
important to choose the right polymer because each polymer has different crystallinity
and also has different properties.
Figure 1.4 Stages in the deformation of semicrystalline polymer. (a) Two adjacent chain
folded lamellea and interlamellar amorphous material before deformation. (b)
Elongation of amorphous tie chains during first stage of deformation. (c) Tilting of
lamellar chain folds during the second stage. (d) Separation of the crytalline block
segments during the third stage. (e) Orientation of block segments and tie chains with
the tensile axis in final stage [4]
6
1.1.3
MELTING TEMPERATURE, T m AND GLASS TRANSITION
TEMPERATURE, T g IN POLYMER
At the melting temperature, T m , the crystalline of polymers will lose their
structure or melt. T m depends on crystallinity, if crystallinity increases so does T m . The
melting of polymers takes place over a range of temperatures. The melting behaviour
depends on temperature which it crystallizes. Impurities in the polymers also decrease
the melting temperature.
The stiffness of the chain controlled by the ease of rotation about the chemical
bonds along the chain give the huge effect. The chain flexibility can be lower by the
presence of double bonds and aromatic groups in the polymer backbone and finally
increase the T m . The size and type of side groups influence the chain rotational freedom
and flexibility and raise of T m . Table 1.1 showed that PP has a higher T m than PE which
are 175°C and 115°C respectively. It is because methyl group in PP is larger than the
hydrogen atom in PE and this increase the T m [3].
Glass temperature, T g is the temperature where the polymers lose their structural
mobility of polymer chains and become rigid glass.
The polymer will behave in
increasingly brittle manner if the temperature drops below T g and becomes more rubberlike if the temperature rise aboveT g . The T g also known as the temperature at which the
molecules of the material move enough so that can be processed and polymers tend to be
brittle below the T g [6]. The value of T g depends on molecular characteristics that affect
chain stiffness, and all factors are same as the T m . Thus, T m and T g is important during
selecting materials for various applications.
Figure 1.5 is the T m and T g for amorphous, semicrystalline and crystalline
materials respectively. For crystalline material (curve C), there is discontinuous changes
in specific volume at T m while the amorphous material (curve A), the curve is
continuous. For the semicrystalline materials, the behaviour is intermediate between
crystalline and amorphous [4].
7
Melting process involves the breaking of inter-chain bonds, so the glass and
melting temperature depend on chain stiffness, molecular shape and size, side branches
and cross-linking [5]. The right temperature must be setup because high temperature
may degrade the polymer or destroy the chain and additives may decompose. If
temperature is too low, the structure fails to achieve the required homogeneity and thus
will reduce impact resistance [6]. Dwell time in process also play crucial role. If higher
dwell time given, thermal decomposition may take place even the melt temperature is
correct but if too short, the melt will not have time to fully homogeneous.
Figure 1.5 Specific volume versus temperature for amorphous (curve A), semicrystalline
(curve B) and cystalline (curve C)[4]
8
Table 1.1 Melting and Glass Transition Temperatures for Some of Common Polymeric
Materials [3,9]
Polymers
1.1.4
T m (ºC)
T g (ºC)
Polypropylene (PP)
165
-18
Poly-lactic Acid (PLA)
175
55 - 60
Polyethylene (PE)
115
110
Polytetrafluoroethylene (PTFE)
327
-97
Polystyrene (PS)
240
100
Polycarbonate (PC)
265
150
POLYMER BLENDS
Polymer blends occur when two or more different polymers mixed together.
There are two types of polymer blends which are miscible and immiscible polymer
blends. For miscible polymer blends, the miscibility and homogeneity extend down to
the molecular lever which is no phase separation occur to the polymer. For immiscible
polymer blends, there are phase separations occurs and sometimes called compatible
blends. The compatible blends are also polymer alloy [11,14]. The light scattering, Xray scattering, and neutron scattering can be used in order to investigate the phase of
polymer blends.
In polymer blends, there are either homogenous or heterogeneous miscibility.
Both polymers lose their identity and usually the new properties are arithmetical average
of the polymer in homogeneous but in heterogeneous, the properties for involved
polymers are present [12]. The weakness of the one polymer can affect the strengths of
the polymer. But still, the blends can have better properties than individual element.